Circular nano-indentation in particle-reinforced metal matrix composites: Simply uniformly distributed particles lead to complex nano-indentation response

The indentation response of aluminum–matrix SiC particle-reinforced metal matrix composites (PR-MMCs) impressed by a circular indenter has been numerically analyzed under the two-dimensional discrete dislocation plasticity combined with the ANSYS® finite element software. Dependence of the nominal hardness HN on multiple factors, including the particle size, the particle area fraction, the matrix thickness between the indenter and the particle, the indentation location as well as the particle shape, is addressed in detail. Herein, we show that the nano-indentation response of the PR-MMCs is strongly associated with the particle area fraction of PR-MMCs as well as the blocking of dislocation free gliding within the matrix. At a high particle area fraction of 25%, HN increases with the decrease of the particle size due to the increasing blocking effect of particles on the dislocation gliding. However, at a low particle area fraction of 9%, a reverse dependence of HN could be observed, which is attributed to the formation of long free-slip bands in the matrix.